Abstract:A new algorithm named optimal matching based on spatial relationship in local regions for content-based image retrieval is proposed in this paper. The algorithm first employs the symbol mapping model to reduce a symbolic image to a l-D representation, and then uses the principle of nearest distance within equal angle region for searching nearest nodes, takes the center point for dividing images into sub-regions, and applies the breadth-first traversal algorithm in graph theory to perform graph matching. Finally, it uses the defined similar distances between local regions and among different graphs to compute the similarity and to retrieve images based on inner spatial relationship. Based on these algorithms, a prototype system for analyzing the position of players in basketball game is constructed. The effectiveness of image retrieval based on spatial relationship is verified in this system by using some real data.